A well known staple remover comprises two pivotally attached parts that have cam surfaces at their respective ends. The device is held in the hand of a user, and the two parts are squeezed together by the user after the tips of the cams have been engaged with the staple. The bight of the staple is moved along the cam surfaces as the parts move toward each other to lift the staple and remove it from an object.
A common problem with this type of staple remover is that the staple is pulled from the object in an uneven manner, which typically results in one leg remaining lodged in the object while the other leg is free. Another, similar problem is that the staple is often broken by the action of the puller, leaving the part remaining in the object separate from the remainder of the staple. The flat parts of the known staple remover adjacent the cam surface do not permit secure gripping of the staple as this would interfere with the removal of subsequent staples.
Various arrangements have been proposed to allow the part of the staple that remains in the object to be grasped by the staple puller in a manner that does not rely on the action of the cam surfaces. One such arrangement is shown in U.S. Pat. No. 3,311,346 (Almond, Jr.). The staple remover according to this patent includes a block mounted in each of the channel-like parts of the staple remover such that the staple can be grasped between the blocks and pulled out. U.S. Pat. No. 4,921,216 (Krulich) shows a staple remover of the same general type wherein one of the cam surfaces has a notch for receiving the staple and for holding the staple securely by a force applied by the cam surface of the other part.
Arrangements similar to that of Krulich are shown by U.S. Pat. Nos. 858,257 (Breiding), 2,431,922 (Curtiss), and 4,869,464 (Davidson).
U.S. Pat. No. 4,944,491 (Kirk) teaches a staple puller wherein the cam surfaces are flanked by protrusions that expand the legs of the staple. U.S. Pat. No. 499,637 (Knight) shows yet another type of staple extractor.
The prior art staple pullers having gripping parts do not provide effective means for releasing or ejecting a staple from the gripping parts. It is difficult, therefore, in this type of device to remove a plurality of staples in succession without manually clearing each pulled staple from the device. Moreover, the devices having gripping elements are not easily manufactured, requiring assembly of several parts or complicated stamping of the parts.